Pipette



M. C. SANZ April 26, was

PIPETTE Original Filed Jan. 6, 1961 FIG.1

I NVENTOR. flmz/aaavos SA/vz.

United States Patent 3,247,866 PIPETTE Manuel Claude Sanz, 46 Avenue Tonrnay,

. Geneva, Switzerland Original application Jan. 6, 1961, Ser. No. 81,116, now Patent No. 3,118,306,'dated Jan. 21, 1964. Divided and this application Nov. 12, 1963, Ser. No. 322,916

. 1 Claim. (Cl. 137533) This invention relates to pipettes for transferring predetermined reproducible quantities of liquids.

This application is a division of US. application Serial No. 81,116 filed January 6, 1961, now Patent No. 3,118,- 306, which in turn is a continuation-impart of US. application Serial No. 652,265 filed April 11, 1957, now US. Patent No. 2,974,528. In that patent, there are disclosed pipettes which include the container or reservoir for the liquid to be transferred in reproducible quantities. Such pipettes comprise a measuring tube with one end extending into a chamber into which the liquid from the container or reservoir may be forced; the chamber has an outlet to the atmosphere which may be closed to force liquid from the chamber into the measuring tube and then opened to allow excess liquid to flow back into the reservoir when the outlet to the atmosphere is opened and pressure released. In order to deliver the liquid retained in the measuring tube, the outlet of the chamber is first closed and then pressure is applied to the reservoir which will force the liquid out of the measuring tube.

Among the objects of the present invention is to provide means for automatically closing the outlet of said chamber upon pressure applied to the reservoir and automatically opening said outlet upon release of said pressure.

The objects are attained by providing a very delicate valve means for the outlet of the chamber of said device,

In the drawings:

FIG. 1 is a side cross-sectional view of the chamber portion of a device showinga modified form of valve.

FIG. 2 is a cross-sectional view taken on line 66 of FIG. 1.

FIG. 3 is a cross-sectional view similar to FIG. 1, showing another form of valve.

FIG. 4 is a view taken on lines 88 of FIG. 3.

The chamber of FIGS. 1 and 3 corresponds to the chamber in the pipettes of said Patents 2,974,528 and 3,118,306 and has a tube 7 0 projecting therefrom. Chamber 20" also includes the pipette measuring tube 25, held by plug 24 in opening 23 of said chamber 20". The tube 70 is curved so that its outer end opens downwardly and is fitted with the valve casing 71. The front or lower end 72 of said valve contains the opening 73 and on the inside forms the valve seat for the movable valve membrane 74 which consists, for example, of a disk-shaped membrane cut from a film or thin sheet of impervious material such as polyethylene. The member 76 includes a central opening 77 continuous with the opening of tube 70. The central inner portion of member 76 extends fairly close to the valve membrane 74 to keep said membrane in position but said member 76 has slots 78, 79 extending from the opening 77 to the side of the member which slots prevent the movable membrane 74 from'shutting oif movement of air into the chamber 20". Since the movable valve membrane 74 is very light in weight and has a minimum of inertia, the membrane moves quickly to open the valve when pressure is released within the chamber 20" and does not permit any liquid to be aspirated from capillary 25.

' In the modification of FIGS. 3 and 4 the valve mechanism has a connecting tube 80 fitting in the opening 81 3,247,866 Patented Apr. 26, 1966 of chamber 20". The opening 86 of tube 80 extends through the backing plate 82 which forms a rest portion for the valve member 83. Plate 82 contains channels 84, 85 extending from the opening 86 to the sides thereof so that valve member 83 is not effective in shutting off the flow of air into the chamber 20". The upper end 87 of the valve has an internal flat surface and includes the opening 88. Valve member 83 is formed of two disk shaped membranes 89 and 90 of polyethylene or similar film which are held apart in the center portion by electrostatic repulsion or which are held apart by entrapped air between the completely sealed edges of the membranes. Upon application of pressure to the container and the transfer of such pressure to the chamber 20" the membranes 83 move against the inside surface of top 87 and close the opening 88. At the same time, the membrane valve 83 quickly opens orifice 88 when pressure is released from chamber 20".

The features and principles underlying the invention described above in connection with specific exemplifications will suggest to those skilled in the art many other modifications thereof. It is accordingly desired that the appended claim shall not be limited to any specific feature or details thereof.

I claim:

Valve means adapted to open and close in response to very slight changes in pressure comprising,

a casing including a valve seat on a first side thereof having a central opening and a relatively flat surface surrounding the opening,

said central opening of said first side being open to the atmosphere,

a light movable valve member comprising a membrane of at least one thin impervious plastic film and having area substantially greater than the area of said central opening,

said casing having a second side, which includes a fluid conduit, for limiting the movement of the valve member away from the first side,

said second side of said casing including grooves which connect the fluid conduit to a region beyond the area covered by said membrane whereby said membrane is not effective in stopping movement of fluid outward with respect to the second side, and in combination therewith a chamber to which pressure can be applied connected to said fluid conduit of said second side,

said light movable valve member comprising a pair of disks of plastic film sealed at the edges thereof with gas entrapped therebetween, said disk adjacent the opening of said first side being substantially flat.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 8/ 1959 Great Britain.

ISADOR WEIL, Primary Examiner.

D. H. LAMBERT, Assistant Examiner. 

